Quality assessment of microarray experiments

OBJECTIVES

We describe a quality assurance procedure to maximize the value of oligonucleotide microarray expression profiles.

DESIGN, METHODS, AND RESULTS

Background microarray noise was 82.2+/-54.5 and 51.8+/-12.4 units, respectively, before and after enacting the program (P<0.0001). We also noted improved concordance of microarray expression fold-changes for selected genes with results of RT-PCR validation.

CONCLUSIONS

This multi-step procedure, including quantification of RNA sample degradation and detection of outlier data points, has increased data quality from our microarray facility.

Glucose dependence of the regulated secretory pathway in alphaTC1-6 cells

We have investigated the effects of chronically elevated glucose concentrations on the pancreatic alpha-cell line alphaTC1-6. We show that basal glucagon secretion and proglucagon gene expression were increased in response to high glucose levels. The extent of acute stimulated secretion of glucagon was also increased in response to high glucose, as was the transcription of the prohormone processing enzymes PC1/3 and PC2. The secretion of GLP-1, a proglucagon-derived peptide produced by cleavage of proglucagon by PC1/3, was also increased in response to high glucose. Gene expression profiling experiments showed that a number of components of the regulated secretory pathway were up-regulated at high glucose concentrations, including processing enzymes and exocytotic proteins. Immunoblot analysis showed that the expression of the exocytotic SNARE proteins, as well as that of PC1/3, chromogranin A, and 7B2, were all increased after chronic exposure to high glucose levels. Immunocytochemistry showed no changes in the expression of the mature alpha-cell markers glucagon and brn-4 and no induction of the immature alpha-cell marker pdx-1. We conclude that chronically elevated glucose concentrations up-regulate the regulated secretory response of the alpha-cell.

Optimizing RNA extraction yield from whole blood for microarray gene expression analysis

OBJECTIVES

Microarray analysis of gene expression profiles of blood leukocytes has many potential clinical and research applications.

DESIGN AND METHODS

We used the PAXgene Blood RNA System to prepare RNA from the whole blood of normal volunteers using two incubation times followed by gene expression profiling using the Affymetrix HU133A GeneChip.

CONCLUSIONS

Longer incubation gave a significantly higher RNA yield and samples that were satisfactory for microarray analysis, with excellent pairwise correlations between replicates.

Toxicity and metabolism of subcytotoxic inorganic arsenic in human renal proximal tubule epithelial cells (HK-2)

Arsenic is an environmental toxicant and a human carcinogen. The kidney, a known target organ of arsenic toxicity, is critical for both in vivo arsenic biotransformation and elimination. This study investigates the potential of an immortalized human proximal tubular epithelial cell line, HK-2, to serve as a representative model for low level exposures of the human kidney to arsenic. Subcytotoxic concentrations of arsenite (< or = 10 micromol/L) and arsenate (< 100 micromol/L) were determined by leakage of LDH from cells exposed for 24 h. Threshold concentrations of arsenite (between 1 and 10 micromol/L) and arsenate (between 10 and 25 micromol/L) were found to affect MTT processing by mitochondria. Biotransformation of subcytotoxic arsenite or arsenate was determined using HPLC-ICP-MS to detect metabolites in cell culture media and cell lysates. Following 24 h, analysis of media revealed that arsenite was minimally oxidized to arsenate and arsenate was reduced to arsenite. Only arsenite was detected in cell lysates. Pentavalent methylated arsenicals were not detected in media or lysates following exposure to either inorganic arsenical. The activities of key arsenic biotransformation enzymes--MMAV reductase and AsIII methyltransferase--were evaluated to determine whether HK-2 cells could reduce and methylate arsenicals. When compared to the activities of these enzymes in other animal tissues, the specific activities of HK-2 cells were indicative of a robust capacity to metabolize arsenic. It appears this human renal cell line is capable of biotransforming inorganic arsenic compounds, primarily reducing arsenate to arsenite. In addition, even at low concentrations, the mitochondria are a primary target for toxicity.

Genome-wide insertional mutagenesis of Arabidopsis thaliana

Over 225,000 independent Agrobacterium transferred DNA (T-DNA) insertion events in the genome of the reference plant Arabidopsis thaliana have been created that represent near saturation of the gene space. The precise locations were determined for more than 88,000 T-DNA insertions, which resulted in the identification of mutations in more than 21,700 of the approximately 29,454 predicted Arabidopsis genes. Genome-wide analysis of the distribution of integration events revealed the existence of a large integration site bias at both the chromosome and gene levels. Insertion mutations were identified in genes that are regulated in response to the plant hormone ethylene.

Genome-wide insertional mutagenesis of Arabidopsis thaliana

Over 225,000 independent Agrobacterium transferred DNA (T-DNA) insertion events in the genome of the reference plant Arabidopsis thaliana have been created that represent near saturation of the gene space. The precise locations were determined for more than 88,000 T-DNA insertions, which resulted in the identification of mutations in more than 21,700 of the approximately 29,454 predicted Arabidopsis genes. Genome-wide analysis of the distribution of integration events revealed the existence of a large integration site bias at both the chromosome and gene levels. Insertion mutations were identified in genes that are regulated in response to the plant hormone ethylene.

Evolutionary expansion of CRIB-containing Cdc42 effector proteins

Cdc42, a small GTPase, regulates actin polymerization and other signaling pathways through interaction with many different downstream effector proteins. Most of these effector proteins contain a Cdc42-binding domain, called a CRIB domain. Here, we describe the evolutionary analysis of these CRIB-containing proteins in yeast, worms, flies and humans. The number of CRIB-containing effector proteins increases from yeast to humans, involving both an increase within families and the emergence of new families. These evolutionary changes correlate with the development of the more complex signaling pathways present in higher organisms.

Communicating with terminally ill cancer patients and their families

This qualitative study aimed to investigate whether 4th year undergraduate nursing students raise concerns about communication with terminally ill and dying cancer patients and their families. It focused on factors which could influence students' feelings of insecurity/security when communicating with this group of patients and their families, factors which could influence communication, and whether students felt adequately prepared for this kind of nursing. The research involved interviewing 12 student nurses in their 4th year of their undergraduate education at a Scottish university using content analysis for analyzing the data. Five themes and 13 sub-themes emerged from this analysis. The findings revealed that communicating with terminally ill and dying cancer patients in the acute setting is difficult for student nurses and issues about death and dying tended to be ignored. While it was found that university lectures about death and dying were helpful, lack of support and guidance within the clinical setting was a major concern.

The effects of sulfur, thiol, and thiol inhibitor compounds on arsine-induced toxicity in the human erythrocyte membrane

The mechanism of arsine (AsH(3)) toxicity is not completely understood. The first cytotoxic effect of AsH(3) is disruption of ion homeostasis, with a subsequent hemolytic action. The only accepted treatment for AsH(3) toxicity is exchange transfusion of the blood. In this study the effect of sulfur, sulfur compounds, thiol-containing compounds, and thiol inhibitors on AsH(3)-induced disruption of membrane transport and hemolysis in human erythrocytes was investigated in vitro. Elemental sulfur, sodium thiosulfate, 5, 5'-dithio-bis(2-nitrobenzoic acid), and meso-2,3-dimercaptosuccinic acid were successful in delaying hemolysis, but the most successful agent was the sulfhydryl inhibitor, N-ethylmaleimide (NEM). This indicated that sulfhydryl groups, possibly membrane sulfhydryls, are major factors in the hemolytic mechanism of AsH(3). Measuring intracellular ion concentrations tested the effect of NEM on AsH(3)-induced disruption of membrane transport. AsH(3) alone caused all ions tested to flow with their concentration gradients: Intracellular K+ and Mg++ decreased, whereas Na+, Cl-, and Ca++ increased. NEM was unable to prevent ion loss except for Ca++, whose increase was prevented for 1 h after AsH(3) treatment. The influx of Ca++ in AsH(3)-treated erythrocytes is an irreversible event leading to hemolysis. Reduction of oxygenated hemoglobin to carboxyhemoglobin completely inhibited AsH(3)-induced hemolysis. In addition, AsH(3) and NEM had no direct chemical interactions. We concluded that membrane sulfhydryl groups are likely targets of AsH(3) toxicity, with NEM being able to prevent AsH(3)-induced hemolysis.

LLC-PK1 cells as a model for renal toxicity caused by arsine exposure

The mechanisms of arsine (AsH3) toxicity are not completely understood. Studies were undertaken to determine AsH3 and arsenite [As(III)] toxicity in a renal tubular epithelial cell line to model kidney dysfunction caused by AsH3 exposure. The hypothesis was that As(III) is the toxic metabolite responsible for the renal toxicity of AsH3. There was a concentration- and time-dependent toxic response after As(III) incubation. As(III) produced significant LDH leakage as early as 1 h and intracellular potassium loss at 5 h. AsH3 produced no changes in these parameters. AsH3 affected neither potassium nor LDH levels over 24 h and up to 1 mM AsH3 concentration. In this system, As(III) induced LDH leakage before K+ loss. Oxidative stress-like toxicity effects were also studied by determining levels of glutathione (GSH), glutathione disulfide (GSSG), and heat-shock protein 32 (Hsp32) levels. GSH levels were not markedly affected by any arsenical over a 6-h period or up to 100 microM concentration of the arsenical. However, 100 microM AsH3 significantly increased GSSG levels as early as 30 min and reached a maximum at 2.5 h. Incubation with 10 microM AsH3 was sufficient to significantly increase GSSG levels. As(III) had no marked effect on GSSG. Both arsenicals (50 microM) produced a slight increase (about threefold) in Hsp32 levels after 4-h incubation. These results showed that unchanged AsH3 produced oxidative stress-like toxic effects without producing cell death. However, similar As(III) concentrations induced the stress response and were toxic to the cells. These data indicated that AsH3 is not directly toxic to LLC-PK1 cells.

The evolving educational needs of nurses caring for the older adult: a literature review

Recent changes in long-term care policies in the United Kingdom have resulted in many more older patients/clients, previously nursed in long-term hospital facilities, now being cared for in the community. This change has had a significant impact on nurses, forcing many to make the transition from working in hospital to within the community. This transition calls for appropriate professional educational preparation to enable these nurses to undertake their new roles effectively. The literature search that forms the basis for this paper revealed relatively little material focusing specifically on the educational needs of such nurses in transition. However, literature that addresses the needs of nurses caring for the older individual in the acute setting, and in the community environment, was found and is explored.

Monomethylarsonous acid (MMA(III)) is more toxic than arsenite in Chang human hepatocytes

Methylation has been considered to be the primary detoxication pathway of inorganic arsenic. Inorganic arsenic is methylated by many, but not all animal species, to monomethylarsonic acid (MMA(V)), monomethylarsonous acid (MMA(III)), and dimethylarsinic acid (DMA(V)). The As(V) derivatives have been assumed to produce low toxicity, but the relative toxicity of MMA(III) remains unknown. In vitro toxicities of arsenate, arsenite, MMA(V), MMA(III), and DMA(V) were determined in Chang human hepatocytes. Leakage of lactate dehydrogenase (LDH) and intracellular potassium (K(+)) and mitochondrial metabolism of the tetrazolium salt XTT were used to assess cytotoxicity due to arsenic exposure. The mean LC50 based on LDH assays in phosphate media was 6 microM for MMA(III) and 68 microM for arsenite. Using the assay for K(+) leakage in phosphate media, the mean LC50 was 6.3 microM for MMA(III) and 19.8 microM for arsenite. The mean LC50 based on the XTT assay in phosphate media was 13.6 microM for MMA(III) and 164 microM for arsenite. The results of the three cytotoxicity assays (LDH, K(+), and XTT) reveal the following order of toxicity in Chang human hepatocytes: MMA(III) > arsenite > arsenate > MMA(V) = DMA(V). Data demonstrate that MMA(III), an intermediate in inorganic arsenic methylation, is highly toxic and again raises the question as to whether methylation of inorganic arsenic is a detoxication process.

Systemic indicators of inorganic arsenic toxicity in four animal species

The effect of arsenic compounds depends on the chemical form and is specific for certain organs. The lack of specific biological indicators for the effects of each arsenic species makes it difficult to differentiate their toxicity. Five prospective biological indicators of systemic toxicity were examined at time points ranging from 15 min to 24 h using male Sprague-Dawley rats, B6C3F1 mice, Golden-Syrian hamsters, and Hartley guinea pigs, following intraperitoneal dosing with 0.1 and 1 mg/kg sodium arsenite. Rats and mice were also dosed with 1 mg/kg sodium arsenate. Total blood arsenic levels were determined in all animal species to show that exposure occurred and as an index of the severity of the change is an indicator of toxicity. Total blood arsenic levels were increased in all animal species. This increase was dose, arsenic species, and animal dependent. Renal pyruvate dehydrogenase activity was significantly decreased at early time points in mice, hamsters, and guinea pigs, and at later time points in rats dosed with arsenite. Rats and mice dosed with arsenate also exhibited PDH decrease at early time points. Blood hematocrit and glucose were increased in the rat and guinea pig, respectively, after arsenite administration. Creatinine and urea nitrogen were found to be unresponsive to arsenic in most animal species. Data suggested that the mouse and secondly the hamster appear to be the most appropriate animal models for the study of acute arsenic toxicity.

Structural alterations in the rat kidney after acute arsine exposure

The mechanism of arsine (AsH3) toxicity is not completely understood. In this investigation, the toxicity of AsH3 and AsH3-produced hemolytic products was determined in primary culture of renal cortical epithelial cells and in the in situ isolated rat kidney. The objective of this study was to model kidney dysfunction caused by AsH3 exposure. The hypothesis was that unchanged AsH3 and AsH3-produced hemolysate that may contain arsenite (As(III)) as metabolite are both responsible for renal toxicity. Toxicity in isolated cells was determined by 2, 3-bis[2-methoxy-4-nitro-5-sulfophenyl]-2H-tetrazolium-5-carboxa nilide inner salt (XTT) bioreduction, intracellular potassium (K+), and lactate dehydrogenase (LDH) leakage. Data from XTT bioreduction showed that most toxicity occurred at 1 hour and was independent of the arsenic species. At 4 hours, the observed toxicity depended on the arsenic species and was generated by As(III). In the isolated cells, the As(III)-spiked hemolysate produced similar toxicities with regard to intracellular K and LDH. The AsH3-hemolysate only affected LDH at 1 hour. Unchanged AsH3 was very toxic to the isolated rat kidney. In this system, after 10 minutes exposure to AsH3, the effects of toxicity were observed mainly in the glomerular and peritubular endothelial cells. Tubular epithelial cells also presented early signs of toxicity. The AsH3-hemolysate was not toxic after a 1 -minute exposure. These data suggested that early cytotoxicity caused by unchanged AsH3 results in kidney dysfunction, produced by AsH3, and later by the formation of a hemolysate that may contain As(III). These data may be important in understanding the renal toxic effects after AsH3 intoxication.

Absorption and disposition of cobalt naphthenate in rats after a single oral dose

The absorption and disposition of inorganic cobalt salts after oral administration have not been completely characterized. The objective of this project was to investigate the absorption and disposition of cobalt naphthenate in Fischer 344 rats following a single oral dose. Cobalt naphthenate was given orally at 3 doses: 0.333, 3.33, or 33.3 mg Co(II)/kg. Tissues, urine, and feces were collected over a 36-h period from the low- and high-dose groups; blood was collected from all 3 dose groups. The majority of the dose in both the low- and high-dose groups was excreted in the feces (42% and 73.1%, respectively), indicating that cobalt was incompletely absorbed from the gastrointestinal tract following oral dosing. The percent of the dose excreted in the urine was similar for low and high doses (31.8% and 26.3%, respectively). Cobalt concentrations were found to be highest in the liver and kidneys. The blood versus time cobalt concentration curves for the low-dose, intermediate-dose, and high-dose groups were elevated 4- to 5-fold, 14- to 25-fold, and 25- to 60-fold over control blood levels, respectively. The peak plasma concentrations of 0.6 and 1.7 microg Co(II)/ml occurred at approximately 4.3 h for the intermediate-dose group, and 3.3 h for the high-dose group. The terminal elimination half-lives were 24.7 and 24 h for the intermediate- and high-dose groups, respectively. Thus, although the extent of cobalt absorption as indicated by the blood concentrations and areas under the blood-time curves was not proportional to dose, the calculated pharmacokinetic values for the time to peak blood concentration and the apparent elimination rate constants were independent of dose. The amount excreted in the urine was also proportional to the dose. These apparent anomalies were not related to protein binding in blood.

In vitro tissue specificity for arsine and arsenite toxicity in the rat

The mechanism of arsine (AsH3) toxicity is not completely understood. In this investigation, we determined AsH3 and arsenite (AsIII) toxicity in Sprague Dawley rat blood, liver, and kidney. In all systems, there were dose- and time-dependent responses. Red blood cells were very susceptible to AsH3 toxicity. This was demonstrated by an immediate intracellular potassium loss and by hemolysis and lactate dehydrogenase (LDH) leakage that occurred by one h. AsIII concentrations up to 1 mM were not toxic to red blood cells using these indicators. Both AsH3 and AsIII produced toxicity in primary hepatocytes. Both produced significant LDH leakage and decreases in intracellular K+ by 5 h, but AsIII was more toxic than AsH3. At 24 h, both arsenic species showed similar toxicity. In renal cortical epithelial cells, AsH3 produced no effects on LDH and K+ over a 5-h period but produced significant LDH leakage by 24 h. In these cells, AsIII produced significant toxicity as early as in 3 h. These results showed that unchanged AsH3 produced toxicity in tissues, in addition to blood, and that toxicity of arsenicals is arsenic species- and tissue-dependent.

Glutathione, albumin, cysteine, and cys-gly effects on toxicity and accumulation of mercuric chloride in LLC-PK1 cells

Speciation plays a profound if not dominant role in both transport and toxicity of Hg(II). Hg(II) has a high affinity for sulfhydryl groups. The formation constant for Hg2+ and the anionic form of a sulfhydryl group R-S- is > or =10(10) higher than that for the carboxyl or amino groups. The kidneys are the target organ for Hg(II) toxicity and the primary site of Hg(II) accumulation. Sulfhydryl groups have been implicated in both transport and nephrotoxicity; however, the role endogenous thiol compounds play in these parameters is not clear. The roles that albumin, glutathione, and the glutathione-derived complexes cysteinylglycine and L-cysteine play in toxicity and accumulation of HgCl2 were studied in LLC-PK1 cells incubated with different Hg(II):thiol ratios. In cysteine-containing medium, almost all 1:2 Hg(II):thiol complexes protected against Hg(II) toxicity up to 120 microM Hg, increased membrane-bound Hg(II), and decreased intracellular Hg(II) accumulation. In cysteine-free medium, all 1:1 Hg(II):thiol complexes were as toxic as uncomplexed Hg(II), and almost all 1:2 Hg(II):thiol complexes protected at > or =20 microM Hg, except albumin, which protected at < or =20 microM Hg. In cysteine-free but cystine-containing medium, two 1:1 Hg(II):thiol complexes were toxic at > or =80 microM Hg and two provided complete protection. All 1:2 complexes provided protection at 80-160 microM Hg. This investigation used defined media to demonstrate that mercury cytotoxicity in LLC-PK1 cells was dependent on Hg(II) concentration, the ligand, and the presence of a cysteine source for the cells. These effects were only partially explained by intracellular Hg(II) levels.

Disposition, toxicity, and intestinal absorption of cobaltous chloride in male Fischer 344 rats

The absorption and disposition of inorganic cobalt salts after oral administration have not been well characterized. The objectives of this study were to compare in vivo results with cobalt transport through the in vitro everted small intestine and to relate the disposition results to a biochemical indicator of cobalt toxicity. Cobalt chloride was given to male Fischer 344 rats orally at 33.3 mg Co(II)/kg or intravenously at 4.16 mg Co(II)/kg. By 36 h, 74.5% of the oral dose was eliminated in the feces. The liver, kidney, and heart accumulated cobalt to the greatest extent. Following the single oral dose, the blood cobalt concentration-time curve was triphasic, peaked at 3.2 h, and had an absorptive half-life of 0.9 h, an elimination phase half-life of 3.9 h, and a terminal elimination half-life of 22.9 h. Following intravenous administration, 10.1% of the dose was excreted in the feces, indicating that cobalt can be secreted in the bile. Following a single intravenous injection, the concentration-time curve displayed three segments. The first segment, which occurred during the first 4 h, had a rapid half-life of 1.3 h. The second phase, from 4 to 12 h, demonstrated a slower clearance rate with a half-life of 4.3 h. The final and slowest phase, from 12 to 36 h, had a half-life of 19 h. Intestinal jejunal ring experiments indicated that cobalt transport has both active and passive components; however, cobalt transport through the in vitro rat everted duodenum indicated that cobalt transport had almost exclusively passive components with facilitated diffusion. The finding that uptake was saturable may explain the small extent of absorption following oral dosing. Heme oxygenase studies following subcutaneous and intravenous administration resulted in an increase in activity (twofold) over controls, while oral administration did not. We concluded that the extent of cobalt absorption across the gastrointestinal tract is incomplete, and that the concentration administered and the route of exposure may determine its systemic toxicity.

The community gerontological nurse: themes from a needs analysis

With the move of care into the community, the role of nurses caring for older people is changing. However, nurses may not be adequately prepared to cope with this changing role, especially if their training and experience have been primarily hospital based. This study involves an educational needs analysis of registered nurses working in the care of older people in nursing homes and clients' own homes. It is based on focus groups with registered nurses and individual interviews with other professionals, as well as group discussions with older people. The aim of this project is to provide research-based input into the design of a new community care of older people module, to be offered at Napier University, Edinburgh from February 1998. The results presented here consist of three themes or patterns that have emerged from the interview data. The specialist/generalist theme concerns issues of role definition and gerontological specialism. The social/medical theme addresses the shift towards a social model of care when nurses move into the community settings. Finally, the physical health/mental health theme represents the need for greater integration of skills and knowledge from both mental health and general health nursing in the field of community care for older people. The results indicate the need for significant attitude changes and provide a major challenge to educationalists.

The implications of head injury for family relationships

Many of those sustaining head injury recover to the point that they no longer require hospital care. However, the family frequently has to cope with an individual with varying degrees of disability involving physical, psychological, cognitive and social dysfunctioning. This review of the literature briefly considers the possible effects that head injury may have for the injured person before going on to discuss the consequences that such an injury may have for the family of that individual. The family's need for information and education is highlighted and it is suggested that the nurse has an important role to play in this context.

Arsenate toxicity in human erythrocytes: characterization of morphologic changes and determination of the mechanism of damage

Chronic arsenic exposure is associated with alterations in peripheral circulation and vascular disease. Toxicity to the vasculature is documented, but the effect of arsenic on the erythrocyte has not been evaluated. To determine if arsenic was toxic to human erythrocytes and whether this could contribute to vascular disease, human erythrocytes were incubated in vitro with sodium arsenate, As(V), or sodium arsenite, As(III), and assessed for damage. After 5 h of incubation with 10 mM As(V) or As(III), significant cell death (hemolysis) only occurred in the As(V) treated cells. Morphologic changes were assessed by scanning electron microscopy and light microscopy. As(V) induced a classic discocyte-echinocyte transformation extending to the formation of sphero-echinocytes; these changes were concentration dependent. As(III) treatment also resulted in echinocyte formation but less extensive than in As(V) treated cells, and no sphero-echinocytes were formed. The observed damage was consistent with reported changes induced by ATP depletion, and measurement of ATP in these samples confirmed this as a mechanism of damage. As(V) treatment at concentrations as low as 0.01 mM for 5 h significantly depleted ATP, and As(III) was relatively ineffective in causing ATP depletion. Based on these three parameters, the erythrocyte was estimated to be as much as 1000 times more susceptible to As(V) than As(III). ATP is required for the cell to maintain membrane integrity and deform efficiently in circulation. The changes described here could contribute to vascular occlusion, ischemia, and tissue death associated with arsenic circulatory disorders.

Sequence of toxic events in arsine-induced hemolysis in vitro: implications for the mechanism of toxicity in human erythrocytes

Arsine, the hydride of arsenic (AsH3), is the most acutely toxic form of arsenic, causing rapid and severe hemolysis upon exposure. The mechanism of action is not known, and there are few detailed investigations of the toxicity in a controlled system. To examine arsine hemolysis and understand the importance of various toxic responses, human erythrocytes were incubated with arsine in vitro, and markers of toxicity were determined as a function of time. The earliest indicators of damage were changes in sodium and potassium levels. Within 5 min incubation with 1 mm arsine, the cells lost volume control, manifested by leakage of potassium, influx of sodium, and increases in hematocrit. Arsine did not, however, significantly alter ATP levels nor inhibit ATPases. These changes were followed by profound disturbances in membrane ultrastructure (examined by light and electron microscopy). By 10 min, significant numbers of damaged cells formed, and their numbers increased over time. These events preceded hemolysis, which was not significant until 30 min. It has been proposed that arsine interacts with hemoglobin to form toxic hemoglobin oxidation products, and this was also investigated as a potential cause of hemolysis. Essentially on contact with arsine, methemoglobin was formed but only reached 2-3% of the total cellular hemoglobin and remained unchanged for up to 90 min. There was no evidence that further oxidation products (hemin and Heinz bodies) were formed in this system. Based on these observations, hemolysis appears to be dependent on membrane disruption by a mechanism other than hemoglobin oxidation.

Reactive oxygen species do not cause arsine-induced hemoglobin damage

Previous work suggested that arsine- (AsH3-) induced hemoglobin (HbO2) damage may lead to hemolysis (Hatlelid et al., 1996). The purpose of the work presented here was to determine whether reactive oxygen species are formed by AsH3 in solution, in hemoglobin solutions, or in intact red blood cells, and, if so, to determine whether these species are responsible for the observed hemoglobin damage. Hydrogen peroxide (H2O2) was detected in aqueous solutions containing AsH3 and HbO2 or AsH3 alone but not in intact red blood cells or lysates. Additionally, high-activity catalase (19,200 U/ml) or glutathione peroxidase (68 U/ml) added to solutions of HbO2 and AsH3 had only a minor protective effect against AsH3-induced damage. Further, the differences between the visible spectra of AsH3-treated HbO2 and H2O2-treated HbO2 indicate that two different degradative processes occur. The presence of superoxide anion (O2-) was measured by O2(-)-dependent reduction of nitro blue tetrazolium (NBT). The results were negative for O2-. Exogenous superoxide dismutase (100 micrograms/ml) did not affect AsH3-induced HbO2 spectral changes, nor did the hydroxyl radical scavengers, mannitol, and DMSO (20 mM each). The general antioxidants ascorbate (< or = 10 mM) and glutathione (< or = 1 mM) also had no effect. These results indicate that the superoxide anion and the hydroxyl radical (OH) are not involved in the mechanism of AsH3-induced HbO2 damage. The results also indicate that although AsH3 contributes to H2O2 production in vitro, cellular defenses are adequate to detoxify the amount formed. An alternative mechanism by which an arsenic species is the hemolytic agent is proposed.

Environmental health and hazardous waste issues related to the U.S.-Mexico border

Environmental health and environmental quality issues along the U.S.-Mexico border have been of concern for several years. The enactment of the North American Free Trade Agreement and the presence of the maquiladoras (foreign-owned industries using imported raw materials) have intensified those concerns recently. Efforts to assess these issues are complicated by the fact that many of the issues affecting the border region are within federal jurisdiction, but the problems are regional and local in nature. Thus, state and local governments become involved with public concerns about real and potential problems. One major problem is that environmental health data from this region are lacking, particularly from Mexico. Some new agencies such as the Border Environment Cooperation Commission, the United States-Mexico Border Health Commission, and the North American Commission on Environmental Cooperation have joined several existing agencies at the federal and state level to address environmental quality and health. Several studies have been initiated to determine air and water quality, but little is being done in the areas of hazardous waste and health assessment. Several problems are anticipated in the generation of such data, such as its format and accessibility. Data gaps and research needs are discussed.

Inorganic mercury chloride-induced apoptosis in the cultured porcine renal cell line LLC-PK1

HgCl2 is known to be a renal toxin, but its mechanisms of toxicity are not well understood. The cell line LLC-PK1 was used as a model for renal proximal tubule cells, and the effects of different concentrations of HgCl2 were studied. Apoptosis in response to 35 microM HgCl2 was confirmed by observation of morphological features characteristic of apoptotic cells as well as cleavage of chromosomal DNA into fragments of multiples of 200 base pairs. Ten percent of LLC-PK1 cells in a monolayer underwent apoptosis. These cells detached from the culture flask before apoptosis. Measurement of transepithelial resistance (TER) was used as a functional assay of junctional complex integrity in a novel approach to characterize preapoptotic events in this cell line. Monolayers of LLC-PK1 cells that contained apoptotic cells showed a transient decrease in TER followed by a recovery of TER to the initial levels. The decrease in TER was accompanied by a loss of hemicysts within the monolayer. These data indicate a temporary loss of junctional complexes within the monolayer during apoptosis. One hundred micromolar HgCl2 caused all cells to become necrotic within 3 hr. HgCl2 (10 microM) caused some changes in cell morphology, but no cell death.